In the great burst of technology since the 1940's, many hundreds of thousands of useful chemical compounds have been synthesized and produced by industry. Advances in the fields of analytical chemistry and medicine which followed have shown that many of these chemicals can have potential toxic and carcinogenic effects in man and that many of these are present and persistent throughout our environment. One class of chemicals which represent a particularly troublesome problem are those which are resistant or refractory to natural decomposition. Polychlorinated biphenyls (PCB's) are a notorious example of such compounds. These materials, particularly resistant to decomposition even under elevated temperature, were produced and widely used between 1929 and 1977 in many products. In pure or very concentrated form, PCB's were used as dielectric fluids in electric transformers and as such, are still in place. Congress banned further PCB production in 1977 after animal tests indicated that PCB's could cause cancer and other health problems. It has been estimated that 750 million pounds of PCB's alone are still in use or present in some form in the United States today, with many more times that level of other potentially harmful organic compounds.
Further, as war and the threat of war persisted, chemical agents and biologic munitions were developed, such as mustard gas and nerve gas agents, which are now desired to be destroyed. Many of these toxic materials are oxygen-rich or mixed with ordinance propellants or chemicals that create massive energy needs in order to contain the de-toxification process at practical temperatures.
In many cases due to a lack of adequate processes or equipment, the only acceptable "disposal" method for such chemicals and biologic agents was long-term storage or containment underground. This method is not an adequate ultimate disposal technique and has potential for adverse effects on both man and his environment.
Incineration is a potentially valuable method of disposal of toxic organic materials since it is possible in theory to oxidize the compounds to CO.sub.2, H.sub.2 O, SO.sub.2, NO.sub.2, and other innocuous or easily handled materials. Operational problems, the use of fossil fuels, the necessity of high volumes of gas flow, and, perhaps most important, the resistance of some compounds (particularly PCB's) to oxidation under conventional operating conditions have limited the use of incineration as a disposal method.
Chemical reaction of toxic materials to render them harmless is a method of some value in detoxification. It has long been the method of choice for many inorganic materials, such as metals and cyanides, and has obvious potential for use in organic treatment. Chemical methods suffer, however, from high cost requirements for close control of processes and the potential for unexpected byproducts.
The present invention is characterized by a solar collector concentrating and focusing the sun's energy into a reaction vessel which is capable of containing the mixing solids, liquids, or gases and exposing these materials to the solar energy for a time sufficient to accomplish breakdown of chemical bonds. The hazardous and toxic wastes or the decomposition products can then be further reacted with, for example, oxygen, to complete the destruction process. Thus, a principal object of the present invention is to provide a method for destruction of hazardous and toxic materials through the application of concentrated solar energy.
A further object of this invention is to use the high intensity specific wavelength energy present in concentrated sunlight to break chemical bonds and accelerate decomposition of chemical compounds. The present invention also has the object using the intense thermal energy present in sunlight to obtain temperatures in excess of those created by combustion systems, which temperatures rapidly decompose chemical compounds. Still another object of this invention is to obtain these high temperatures but also minimize the requirement for air or other gaseous throughput so as to also minimize the large volumes of exit gas common to combustion systems. The present invention also has the object of providing the above objects in the treatment of solid, liquid or gaseous materials.
Photochemical degradation appears to be a primary pathway for natural environmental renewal. Specific wavelength energy can be absorbed by certain chemical bonds to break these bonds. For a given compound, the change in concentration of the organic material over time has been found to be directly proportional to the original concentration, so that a rate constant can be determined to provide an equation. That rate constant has been found to be directly proportional to the intensity of the sunlight applied to the concentration of organic material. Therefore, the rate of destruction of the compound is proportional to the intensity of the sunlight.
The present invention provides means for contacting a compound such as an organic material with sunlight which is concentrated many thousands of times.
The chemical reaction for destruction of an organic compound may be accelerated by addition of heat. Specifically, the rate constant for a chemical reaction increases in an exponential manner with temperature. For many common reactions, the effect of this relationship is that reaction rates can be double or triple with a temperature increase of 10 degrees Centigrade.
The present invention provides means for heating the reaction vessel containing a compound such as an organic material and permits doing so without an external combustion process or other man-made energy source which may add materials which in turn would have to be safely exhausted. The present invention may, as an alternative, be used to supplement a man-made energy source.
The process of the present invention employs the entire frequency range of radiation from the sun (IRR-UVR). By utilizing the full range of frequencies for energy transfer, the combined photochemical and thermal decomposition of toxic materials is thought to occur at lower temperatures than those developed through thermal transformation alone.
A further object of the present invention is the further enhancement of the basic process by controlling the rate of oxidation throughout the entire transformation process, including such control during the preparation of the toxic material, the presentation of the toxic material for solar de-toxification, and the effluent. Such an enhancement can provide a relatively inexpensive de-toxification process and apparatus since the process or apparatus can operate effectively at lower temperatures and not need as much coolant as required by a process or apparatus requiring the higher temperature for de-toxification.
Other objects and advantages of the instant invention will be apparent in the following specification, claims and drawings.